Green Synthesis of Silver Nanoparticles Using Extracts of <i>Ananas comosus</i>

The biosynthesis of nanoparticles has been proposed as a cost effective and environmental friendly alternative to chemical and physical methods. Plant mediated synthesis of nanoparticles is a green chemistry approach that intercom nects nanotechnology and plant biotechnology. In the present study, synthesis of silver nanoparticles (AgNPs) or (Green-Silver) has been demonstrated using extracts of Ananas comosus reducing aqueous silver nitrate. The AgNPs were characterized by Ultraviolet-Visible (UV-vis) Spectrometer, Energy Dispersive X-ray Analysis (EDAX), Selected Area Diffraction Pattern (SAED) and High Resolution Transmission Electron Microscopy (HRTEM). TEM micrographs showed spherical particles with an average size of 12 nm. The XRD pattern showed the characteristic Bragg peaks of (111), (200), (220) and (311) facets of the face center cubic (fcc) silver nanoparticles and confirmed that these nanoparticles are crystalline in nature. The different types of antioxidants presented in the pineapple juice synergistically reduce the Ag metal ions, as each antioxidant is unique in terms of its structure and antioxidant function. The re- action process was simple for formation of silver nanoparticles and AgNPs presented in the aqueous medium were quite stable, even up to 4 months of incubation. This work proved the capability of using biomaterial towards the synthesis of silver nanoparticle, by adopting the principles of green chemistry.

Preparation and Characterization of SnO2 Nanofibers via Electrospinning

Tin oxide (SnO2) nanofibers are successfully prepared by electrospinning homogeneous viscous solutions of tin acetate in polyvinylpyrrolidone (PVP). The electrospinning is carried out by applying a DC voltage to the tip of a syringe and maintaining the tip to collector distance (TCD), i.e. at DC electric field of 1.25 kV•cm–1. The electrospun nanofibers are calcined between 550℃ and 650℃ for 4 h. Both spun and heat treated nanofibers are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra red spectroscopy (FTIR) etc. XRD analysis of calcined nanofibers confirms the formation of pure tin oxide. TEM study showed that fibers have a polycrystalline structure with multiple nano-grains.

Synthesis of Agnps By Bacillus Cereus Bacteria and Their Antimicrobial Potential

In the present work silver nanoparticles (AgNPs) were synthesized extracellularly by bacteria Bacillus cereus collected from the riverine belt of Gangetic Plain of India. The microbes were isolated, screened and characterized by morphological and biochemical analyses. The silver resistant strain was exposed to different concentrations of silver salt (AgNO3). UV-visible spectrum of the supernatant of cell culture showed absorbance peak of AgNPs at ~ 435nm.The shape and size of AgNPs were ascertained by High Resolution Transmission Electron Micrography (HRTEM), X-ray diffraction (XRD) and Energy Dispersive spectroscopy (EDS). Average size of the synthesized AgNPs was found to be in the range of 10-30 nm with spherical shape. AgNPs were tested against antibacterial potential of some common human pathogens.

Synthesis of Crystalline Ag Nanoparticles (AgNPs) from Microorganisms

Bacteria obtained from the isolates of the biodiversity of riverine coast of Ganga identified as Bacillus Koriensis, when challenged with silver nitrate solution accumulated silver nanoparticles on the surface of its cell wall. These nanoparticles showed an absorption peak at 438 nm in UV-visible spectrum corresponding to the plasmon resonance of AgNPs. The transmission electron micrographs of nanoparticles in aqueous solution showed the production of reasonably monodisperse AgNPs (average particle size: 9.92 &amp;amp;#177;1.311 nm) by the bacteria. X-ray diffraction spectrum of the nanoparticles confirmed the formation of metallic silver.

Defect induced room-temperature ferromagnetism and enhanced photocatalytic activity in Ni-doped ZnO synthesized by electrodeposition

Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.

Effect of Foundation and Non-Homogeneity on the Vibrations of Polar Orthotropic Parabolically Tapered Circular Plates

The effect of Pasternak foundation and non-homogenity on the axisymmetric vibrations of polar orthotropic parabolically varying tapered circular plates has been analyzed on the basis of classical plate theory. Ritz method has been used to find the numerical solution of the specified problem. The efficiency of the Ritz method depends on the choice of basis function based upon deflection of polar orthotropic plates. The effects of different plate parameters viz. elastic foundation, non-homogeneity, taper parameter and that of orthotropy on fundamental, second and third mode of vibration have been studied for clamped and simply-supported boundary conditions. Mode shapes for specified plates have been drawn for both the boundary conditions. Convergence and comparison studies have been carried out for specified plates.

A New Record on Flowering in Harar (<i>Terminalia chebula</i>Retz.) Seedling

Harar (Terminalia chebula), a large deciduous tree belongs to family combretaceae. It grows naturally in greater part of India up to 1500 m elevation. Due to several alkaloids present in fruit, it is used as laxative, purgative and astringent for curing a number of ailments. Keeping in view its medicinal and tanning properties, the authors have been working for the last two decades on various aspects like propagation and development of promising strains of harar. Grafting/budding techniques have been standardized to produce true to type precocious plants which bear flower in two to three years. However, flowering has been observed in three months old seedling, which can be ascribed to biochemical and/or cellular changes. Early flowering is a rare incidence in tree seedlings which otherwise could be very useful for breeding and early evaluation of fruit species.

A Novel Low Temperature Synthesis of KNN Nanoparticles by Facile Wet Chemical Method

Sodium potassium niobate (KNN) (K0.5Na0.5NbO3) nanopowder with a mean particle size of about 20 - 30 nm was synthesized by wet chemical route using Nb2O5 as Nb source. A solution of K, Na and Nb cations was prepared, which resulted in a clear gel after the thermal treatment. Phase analysis, microstructure and morphology of the powder were determined by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). The obtained gel was first analyzed by Thermo Gravimetric Analyzer (TGA) and Differential Scanning Calorimetry (DSC), and then calcined at different temperatures of 400℃, 500℃, 600℃ and 700℃. The X-Ray Diffraction (XRD) patterns of the synthesized samples confirmed the formation of the orthorhombic crystal phase of K0.5Na0.5NbO3 at 500?C, a temperature significantly lower than that typically used in the conventional mixed oxide route. The process developed in this work is convenient to realize the mass production of KNN nanopowders at low cost and suitable for various industrial applications.

Influence of Sintering Temperature on Densification, Structure and Microstructure of Li and Sb Co-Modified (K,Na)NbO₃-Based Ceramics

Polycrystalline samples of Lead free (K0.5Na0.5)1-x(Li)x(Sb)x(Nb)1-xO3 ceramics with nominal compositions (x = 0.040 to 0.060) have been prepared by high temperature solid state reaction technique. X-ray diffraction (XRD) pattern shows that the crystal structure transforms from orthorhombic to tetragonal as Li and Sb content increases. Normal sintering process yield compounds with density ~98.2% of the theoretical value. Densification of the Li and Sb co-doped KNN ceramics might be explained by the liquid-phase sintering. This may be attributed to the low melting temperature of Li compounds that appears to promote the formation of a liquid phase during sintering.

Dielectric and magnetic properties of Ba-,La-and Pb-doped Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) perovskite ceramics

The multiferroic Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3),(where M=Ba(DB),La(DL)and Pb(DP))has been synthesized by using solid-state reaction technique.Effects of Ba,La and Pb substitution on the structure,electrical and ferroelectric properties of Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) samples have been studied by performing X-ray diffraction,dielectric and magnetic measurements.The crystal structures of the ceramic samples have a tetragonal phase.The vibrating sample magnetometer(VSM)measurement shows a significant change in the magnetic properties of Ba-doped Bi_(0.8)Gd_(0.1)M_(0.1)Fe_(0.9)Ti_(0.1)O_(3) as compared to La-and Pb-doped ceramics.It is seen that coercive field(HC)and remanent magnetization(MR)increases with Ba-doped ceramics but decreases for La-and Pbdoped ceramics.

Dielectric,electrical conduction and magnetic properties of multiferroic Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)perovskite compound

This work focuses on the structural,electrical and magnetic properties of Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)ceramics,fabricated by solid state reaction procedure.XRD forms of the samples at RT exhibited perovskite phase through the hexagonal structure at room temperature.Dielectric studies of the materials with frequency at different temperatures(25-400℃)exhibit two dielectric anomalies,first at 175℃(ferroelectric-ferroelectric transition)and second at around 320℃(ferroelectric-paraelectric transition).The Curie temperature moved towards the low side temperature with the increase in frequency.The less value of activation energy got for these samples could be attributed to the influence of electronic contribution to the conductivity.A significant change in the magnetic studies was observed for Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3) ceramic.The impedance analysis confirms the non-Debye type nature of the ceramic and relaxation frequency moved to a higher temperature.The Nyquist plot and conductivity studies showed the NTCR behavior of samples.The highest magnetization field was found at temperature-268.15℃.

Dielectric relaxation and modulus spectroscopy analysis of(Na_(0.47)K_(0.47)Li_(0.06))NbO_(3) ceramics

We have investigated the structure,dielectric and electrical properties of lead-free polycrystalline (Na_(0.47)K_(0.47)Li_(0.06))NbO_(3) ceramics as a function of temperature and frequency in order to understand the intrinsic contribution of grain/bulk and grain boundary effects toward the dielectric response as well as the electrical conduction mechanism in the samples fabricated by microwave sintering method.X-ray diffraction analysis exhibits perovskite structure with orthorhombic symmetry,which is well supported by the Raman spectroscopic analysis.A minor secondary impurity phase of tungsten bronze structure was observed for samples sintered at 1050℃,which gets weaker for samples sintered at 1150℃.Dielectric permittivity was enhanced by 50%,although there was a reduction in the dielectric loss by about 50%at Curie temperature(450℃)for samples sintered at 1150℃.Complex impedance spectroscopic analysis indicated non-Debye-type dielectric relaxation present in the samples,and this phenomenon followed thermally activated process related to hopping mechanism.Nyquist plot showed the negative temperature coefficient of resistance,characteristic of the samples.

Evaluation of structure,dielectric and electrical properties of(Li/Ta/Sb)modified(Na,K)NbO_(3) lead-free ceramics with excess Na concentration

Polycrystalline perovskite structured Li_(0.04)(Na_(0.54+x) K_(0.46))_(0.96)(Nb_(0.81)Ta_(0.15)Sb_(0.04))O_(3) ceramics with x¼0:00,0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering method.The present study relates the role of excess Na addition with the stoichiometry,density,structure,dielectric and ferroelectric properties of the samples.X-ray diffraction(XRD)pattern exhibits single phase orthorhombic structure.The characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO_(6) octahedra and no structural phase transition were observed.This confirms the formation of single phase perovskite structure and is consistent with XRD results.The dielectric permittivity increases about two times,while dielectric loss decreases by four times for χ=0.01 composition.The electrical measurements carried by Complex Impedance spectroscopic analysis suggest negative temperature coefficient of resistance(NTCR)behavior.

Study of the structural and electrical behavior of Bi(Mg,Ti)O_(3)modified(Ba,Ca)TiO_(3)ceramics

The ability of BaTiO_(3)to form solid solutions with different dopants(both iso-and aliovalent)makes it versatile for various applications.In the present study,(Ba,Ca)TiO_(3)(BCT)is modified with Bi(MgTi)O_(3)(BMT)in search for new lead-free ferroelectric material and improve their properties.For this purpose,BCT acts as a main base material and BMT acts as a modifier to fabricate a multifunctional material.In this study,we report the structural and electrical properties of lead free piezo-ceramics(1-x)(Ba_(0.8)Ca_(0.2))TiO_(3–x)Bi(Mg_(0.5)Ti_(0.5))O_(3)with x=0.2,0.4,0.5 prepared by solid-state sintering technique.Single perovskite phase with tetragonal structure is obtained for all the compositions,which is reconfirmed by the Raman Spectroscopic study.Dielectric study confirm the temperature stable behavior of the dielectric permittivity values above 300℃.The dielectric constant value decreases with increase in BMT doping content.Impedance Spectroscopic study confirms non-Debye type dielectric relaxation in the specimen.The Nyquist plot and conductivity studies show the negative temperature coefficient of resistance behavior(NTCR)of the samples.

IMPEDANCE AND MODULUS SPECTROSCOPY CHARACTERIZATION OF SODIUM-BISMUTH TITANATE-BASED LEAD-FREE FERROELECTRIC MATERIALS

In this paper,we present impedance spectroscopy of Sodium Bismuth Titanate-based materials belonging to(1-x)TNa_(1/2)Bi_(1/2)TiO_(3)-xBaTiO_(3)(x=0.04)(NBT-BT)system.NBT-BT ceramics are prepared by high temperature solid-state reaction method.X-ray diffraction technique showed single-phase polycrystalline sample with an ABO3 perovskite structure.Dielectric behavior and the impedance relaxation were investigated in a wide range of temperature(room temperature(RT)-500℃)and frequency(1 kHz-1 MHz).A broad dielectric constant peak was observed over a wide temperature range around the phase transition temperature.The complex impedance plot exhibited one impedance semicircle identified over the frequency range of 1 kHz-1MHz,which is explained by the grain effect of the bulk.The centers of the impedance semicircles lie below the real axis,which indicates that the impedance response is a Cole-Cole type relaxation.